A head-mounted display (also called the HMD hereunder) is worn on the head of a user to provide the user with a virtual reality (VR) world. In recent years, there have been applications that allow the user to play video games while watching the screen displayed on the HMD. Existing non-portable display devices such as the television set let the user view an extended visual field range outside the screen. This may prevent the user from concentrating on the screen or from getting the sense of immersion in the ongoing game. In contrast, wearing the HMD enables the user to experience a higher sense of immersion in the visual world and thereby boosts the entertaining nature of the video game. If the HMD is configured to have a head-tracking function that updates the display screen in a linked manner with the attitude of the user's head, the sense of immersion in the visual world is further enhanced.
Recent years have witnessed the widespread use of omnidirectional cameras (360-degree cameras) that capture full-azimuth 360-degree panoramic photos. Also, development is underway on unmanned flying objects capable of being remotely piloted. Multiple cameras mounted on such a flying object can capture full-azimuth panoramic photos from the air. If a full-azimuth panoramic photo captured in that manner is displayed on the HMD and if the screen for the display is updated in a linked manner with the attitude of the user's head, the user wearing the HMD is expected to experience the sensation of almost being in the real world.